Conventionally, Raman microscopes, which obtain an image by detecting Raman scattered light that is produced when a laser beam has been applied to a sample, have been known. With a Raman microscope, molecules included in a sample can be identified and the two-dimensional distribution of those molecules can be observed from the Raman scattering spectrum of the sample.
In Japanese Patent Application Laid-open (JP-A) No. 2011-158413, for example, there is disclosed a laser microscope device including: two optical paths that guide pulse laser beams having two different frequencies that have a frequency difference equal to the frequency of a specific molecular vibration of a molecule in a sample; multiplexing means that multiplexes the pulse laser beams guided thereto on the two optical paths; frequency modulating means that is disposed on at least one of the two optical paths and modulates the frequency dispersion amounts of the pulse laser beams guided on the two optical paths; pulse laser beam amplitude modulating means that is disposed on at least one of the two optical paths and modulates the amplitudes of the pulse laser beams guided on the two optical paths; and modulation signal detecting means that condenses, in the sample, the two pulse laser beams multiplexed by the multiplexing means and detects, in synchronization with the modulation by the pulse laser modulation unit, stimulated Raman scattering produced from the specific molecular vibration of the molecule in the sample.
However, the microscope image obtained by a Raman microscope is a two-dimensional image, and the distribution of molecules in the depth direction of the sample cannot be closely observed, even if the focal depth direction is changed, because the signals from all of the optical paths of the laser beams are superposed.